(1) Field of the Invention
The present invention relates to a recording medium in compliance with next-generation DVD standards, in particular to a stream number table defining one or more audio streams that are playable in a predetermined section of a video stream.
(2) Description of the Related Art
In recent years, the next-generation DVD standards, for example, the Blu-ray Disc standard and the HD DVD standard, have been established, familiarizing users with high definition and high quality sound optical discs. In these optical discs, multiple audio streams (e.g., 32 audio streams) are recorded in an attempt to support every combination of encoding format, channel number, and language attribute.
Here, the encoding formats include such as Dolby AC3, Dolby digital Plus, MLP, DTS, DTS-HD, and Linear PCM, and the numbers of channels include such as mono, stereo, and multi-channel.
These optical discs are also recorded with playlist information that includes one or more playback sections (play items) each of which is defined by a playback start point and a playback end point on the time axis of a video stream.
The audio streams recorded on such an optical disc are not playable in every playback section of the video stream. For each playback section, playable audio streams are defined.
This is realized by registering stream numbers of the audio streams that are playable in each playback section into the stream number table corresponding to the playback section.
A playback apparatus selects, in accordance with its playback capability and status setting, the most suitable audio stream to play back out of the audio streams registered in the stream number table corresponding to the playback section (audio stream selection function), and plays back the selected audio stream.
Here, an ordinary audio stream selection function (see Patent Document 1) is described. When selecting an audio stream, the playback apparatus judges, for each of the multiple audio streams registered in the stream number table, which of the following three conditions are satisfied: the playback apparatus has capability to play back the audio stream (condition A); the language attribute of the audio stream matches the language set in the playback apparatus (condition B); and the channel attribute of the audio stream matches the channel attribute set in the playback apparatus (condition C). After that, depending on a pattern of the conditions judged to be satisfied, the playback apparatus assigns a priority to each audio stream, selects one among the multiple audio streams based on the priority, and plays back the selected audio stream.
Specifically, if there is an audio stream that satisfies all of the conditions above, such an audio stream is selected and played back.
If there is no audio stream that satisfies all of these conditions, an audio stream that satisfies the conditions A and B is selected.
If there is no audio stream that satisfies the conditions A and B either, an audio stream that satisfies the conditions A and C is selected.
If there is no audio stream that satisfies the conditions A and C either, an audio stream that satisfies the condition A is selected.
Here, if there are a plurality of audio streams assigned the highest priority, the audio stream to be played back is determined in accordance with the order of the stream numbers in the stream number table. Specifically, the playback apparatus selects the audio stream among the audio streams with the highest priority that is the first in the order of entry in the stream number table.